1. Field of the Invention
The present invention relates to a thrust termination device of a solid rocket motor, which terminates the net thrust by the reverse thrust of the rocket motor produced from the emission of the combustion gas through the opened thrust termination port in the reverse direction, when the stage separation signal is transferred at the normal thrust state of the rocket motor, in particular, to a thrust termination device for a rocket motor, which can contrive to accomplish the structural safety and the mechanical sealing performance at the combustion chamber condition of the high temperature and high pressure, and easily remove the thrust termination device even at the low pressure state and open the trust termination ports successively with very small impacts when the thrust termination is commanded.
2, Background of the Related Art
In general, the solid rocket motor comprises a combustion chamber for combusting solid propellant, and a nozzle for the exit of exhaust gases which makes acceleration of rocket in the opposite direction to the gases flow direction. And the thrust, which is the product of acceleration and mass of rocket, have same direction of acceleration of rocket motor.
There have been developed several kinds of rocket motors, and the principle and mechanism of propulsion are different for each rocket motor. The most widely used rocket motor among them is a chemical rocket motor with an energy source of chemical reaction (combustion) of solid propellant or liquid propellant.
For instance, in a rocket motor using the solid propellant as a fuel, ignition of the solid propellant is performed by a igniting device, and gases produced from the combustion of the solid propellant are exhausted through the outlet of the nozzle, and the retroaction against exhausted gases becomes the thrust of the rocket motor in the normal propulsion state till the practice of the command for the thrust termination. Thus, the rocket motor is provided with a thrust termination device for producing thrust opposing to the thrust of the nozzle so as to neutralize the normal thrust of the nozzle.
When the rocket motor provided with the thrust termination device as described above is schematically reviewed, it comprises a combustion tube for a combustion chamber with a solid propellant charged; a nozzle mounted at the rear of the combustion tube; a dome portion of the combustion tube formed at the front side of the combustion tube; an igniting device mounted at the center of the dome portion of the combustion tube toward the combustion chamber; and a plurality of thrust termination devices mounted at the dome portion of the combustion tube.
According to the rocket motor, normal thrust can be produced at the nozzle at the normal state, however, in this instance, a thrust termination port formed at the dome portion of the combustion tube to communicate with the combustion chamber is maintained to be closed by the thrust termination device. Further, when the command of thrust termination is practiced, the thrust termination port closed by the thrust termination device is instantly opened to produce thrust greater than the normal thrust of the nozzle through the thrust termination ports to thereby impede the forward movement of the rocket motor and reduce the pressure in the combustion tube, so that forward thrust cannot be produced any more in the rocket motor. In this instance, the sum of the sectional areas of the opened thrust termination ports is greater than that of the sectional area of the nozzle throat to thereby make the thrust produced from the thrust termination port greater than the normal thrust of the nozzle, so that the movement of the rocket motor in the forward direction can be impeded.
Conventionally, a Pyrotechnic devices (explosion bolt) described in U.S. Pat. No. 5,400,713 are mostly used in the thrust termination device.
In this regard, it is required for the thrust termination device to be sufficiently safe in structure before the operation, operated rapidly at the operation and reproduced completely. However, when the thrust termination device such as the pyro device was operated, there were produced substantially big impacts, and fragments of the operated device were dispersed, so that the missile had to be affected from the substantial impact during the operation of the thrust termination device to thereby affect badly to the flying stability of the missile and the precision of the control after the thrust termination.
Accordingly, it is very important to reduce the magnitude of impacts at the time of the operation of the thrust termination device.